This is a new Phase I application from BioPhysics Assay Laboratories, Inc. a company founded in 1997 with four employees that proposes to validate and further develop a novel method to measure bile acid transport. The project will focus on cholic acid labeled with different stable isotopes via two different chelates. Experiments in this phase I proposal will seek to evalulate labeling efficiency, overall charge, stability to incubation in buffer with temperature variation, stability to challenge with competing chelates and in a serum environment, sensitivity of detection, and retention of biological activity using isolated hepatocytes. The overall goal is to develop an easy to use and cost effective labeled bile acid assay kit, suitable for research and clinical applications. There is no current routine assay to perform this function. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE